XL1200 won't crank

Newbie here,

In the 4th year running a XL1200 with no problems. But last year {September} we had issue where it would only run {smooth and with full power} for 30-50 seconds and then stall. No warning lights, no buzzers going off. We'd let it sit for 20-30 seconds and it'd start right back up and again run for 30-50 seconds. So we trailered it and put it on the long list of thing to fix but... never got to til now.

Now I'm trying to crank it after pulling and charging the battery for the first time this season but it don't want to crank at all. I put a booster jumper on the battery and got it turn slightly with the plugs out.

So I sprayed WD40 in the Cylinders thinking its gunked up. Was this UNTHINKABLY bad?

This unit (and its brother the GP1200R) were garage kept all winter but I did NOT do anything but pull the batteries for the winter. ( a mild Texas winter)